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Old 11-29-2007, 04:35 PM   #1
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Default Boost Creep on an FMII

Hard to find a place to put this in the categories. Hope this is ok.

I've had an FMII with a link piggy on my car for about ever, it's a 2000 with some decent headwork and 3" open exhaust. I'm running 97 pistons (9.0:1) and some carillo H rods I got really cheap, on the street on California 91.

I got the new FM intercooler set up as it actually seemed to be well designed - aside from being a bit smaller than it could be and perhaps taking an extra bend than it absolutely needs, it is alright, and fixes the worst issue of the old kit.

However, I'm getting ridiculous boost creep now. I aim for 10-11 psi, settle for 12. But on a cold night, I'm getting in the 14-15psi range, and the poorly run link piggy is going way down to 13.3:1 AFR's, which is scarey to say the least (at full revs and boost creep)

So, does anyone have any ideas on what to DO about it? Is there a good wastegate actuator for this? Has someone ground out the wastegate flapper with sucsess?

Yes, I know I need another computer, but that's for another thread. Thanks everyone!
-Abe.
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Old 11-29-2007, 04:48 PM   #2
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Abe, my man. Haven't seen you since The Puke.

Not that I have anything useful to contribute at all to this particular thread, but good to hear it's still running reasonably well.
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Old 11-29-2007, 04:56 PM   #3
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running an EBC should be able to tune it out.

you could port the wastegate outlet, or sell the LINK for a Megasquirt with EBC mod
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Old 11-29-2007, 08:49 PM   #4
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Sure, sure, EBC is fine, but the issue is boost creep: Wastegate all the way open, still getting more boost than I want. Even with the rod unhooked I get like 8 psi if I load the engine enough and take it to redline, and that was before the intercooler upgrade.

I was hoping someone had pics/exepriences opening that up, or could suggest a wate gate actuator that has some real travel to it. Or hybrided an enternal wastegate to the FMII manifold.

Joe! COME OVER FOR FREE BEER sometime soon. The rest of you too, if you want. :-P
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Old 12-11-2007, 08:34 PM   #5
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Time for a small update here, purely conceptual:

I'm also looking into adding a helper spring in the actuator, I'll let you know how it turns out. I noticed the FM provided actuator provides a LOT of movement, it just doesn't let things move. Now, since I could get the wastegate to crack at 7 psi if I put no preload on it, I have a feeling this won't help. But anyway, I wanted to make it easier to move this further.

So, with f=-kx on one side, I thought why not add f = +kx on the other? My idea is simple:


I'm worried it's too simplistic, that the can just won't hold significant pressure and still won't open, but it's easy to try, I have the springs, I just need ten minutes and a washer.
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Old 12-12-2007, 02:44 AM   #6
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Do it and let me know how it turns out. I too am at sea level and apparently the actuators that FM uses have 'known issues' at sea level. On mechanical boost I was getting up to 12psi. I am not sure how this spring idea is going to work but there is another user on the forum who drilled another mounting point for the actuator arm that shortened the lever arm on the wastegate and he had pretty good luck. I just don't want to drill any new holes, so if this works for you, please post. BTY, I am west of long beach if you want to meet sometime to go over ideas.
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Old 12-12-2007, 05:44 AM   #7
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Getting crowded here in SoCal. I like it. :-) Sure, not that I go up there much, but I'm always down for meeting new folks.

I still think there's a lot to be said for moving the fulcrum, I dunno if the little drawing I made made sense (I didn't know I was using the trial version of the software so I couldn't even save it!), but the idea is that you just make a little bracket that drops on the wastegate lever and lets you move a different amount (and with lower effective force).

Maybe I'll just build one, with a dremel if I have to, or bend one up in a vise.

I will definately post about the spring, but... it might be a bit. I'm itching to get this MS in, and I *really* am going to try to mess with as few things as possible at a time. I'd love to try my new coils, and lots of other cool things but I'm taking a huge chill pill till the MS runs.

I'm a little more worried since I can't switch between OEM ecu and MS, with 650 injectors there's no way the OEM will start/idle I think. Topic for another thread.

In the meantime, you can try the spring thing yourself, it's REALLY easy. Pull on the wastegate actuator with your hand, get a spring no more than half as stiff, and just slip it over the pole, then a washer, then the nut and adjustor as normal. You should see the wastegate open earlier (lower mechanical setpoint) and boost-creep less (lower total/final boost).

It's all theory, but it SHOULD only make boost lower and present no harm to your motor. Of course, watch your boost guage, don't do anything dumb, etc. Order something from McMaster and you should have it the next day, but I got mine at a local fastener store so I could feel how strong they were. I'd tell you how strong the one I got is, but... I don't know if it's right yet so what's the point? :-)



P.S. Don't I draw just swell? Really, that's pitiful
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Old 12-12-2007, 11:04 AM   #8
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If that does not work, I can send you one of our actuators and brackets to try.
Stephanie
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Old 12-12-2007, 01:37 PM   #9
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Thanks Steph. Really, I wish I would have found your company sooner.
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Old 12-12-2007, 02:04 PM   #10
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the problem could lie in the link.

Maybe the ebc isn/t tuned correctly?

As you can get the wastegate run to 8 psi...
Your ebc must be able to control everything above...

I have a EBC from a link (piggyback) somewhere... (the origional one, not the newer FM model) If you need it give me a PM (i don't need it)

Looking at the ecu manual: WG BASE: The value of wastegate duty cycle that achieves the desired boost level.

This might be off. If the dutycycle is off the wastgate too little air pressure to open...

The Link piggy back ECU intercepts this signal with the boost control solenoid and manipulates this pressurized air signal to control boost pressure. The solenoid bleeds off some of the pressurized air so that the wastegate actuator “sees” a lower level of boost than what the turbo actually makes. The amount of bleed off is called duty cycle.
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Old 01-12-2008, 01:22 PM   #11
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So did you ever get this working? I didn't get around to it over the holidays and I am on a business trip until February. My 3.636 ring and pinion gear is waiting for me at home, but I would love to get this boost issue straightened out first.

Steph, I might be calling you soon.
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Old 01-12-2008, 05:26 PM   #12
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Did who ever get it working? Mine's been "working" this whole time. 'cept the last week or two, not running any boost at all. I'm hoping to hook this all up again if I can get the FM piggyback manifold off my car and new biggie injectors in, but as far as the drill-and-tap thing it works fine even if it's a bit of a PITA to do.

Otherwise, I'm sure you could make a braket like I showed or come up with some other, easy, way to move the folcrum over.

Otherwise, yeah - you're in for trying a bunch of brackets. Basically, no matter how you look at it there's some fab work invovled.

OR, use the suggestion I got from FM: Try a more restrictive exhaust.

Talk about a deal breaker.
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Old 01-12-2008, 06:07 PM   #13
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To clarify, I was talking about the helper spring concept you were talking about in some posts above.
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Old 01-12-2008, 06:29 PM   #14
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Ah, ok. No, I haven't tried it yet. It creeps, but I tend to run high pressures anyway, so it's not as pressing for me. I'm hoping to get my wastegate hooked up again soon, then I'll be trying to tune down there, and I will likely (find and) install my helper springs then.
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